Fixed holidays (Christmas, July 4, Veterans Day) roll to the next calendar occurrence. Rule-based holidays (Thanksgiving, Memorial Day, Labor Day) use US federal definitions. Always confirm official agency dates for Tax Day and observance shifts.

For historical elapsed time, open /how-long-ago. For clocks right now, open /time.

FAQ

How is Countdown different from Time?

/time is live clocks and zones across the USA. Countdown answers “how many days until …” for holidays and civic dates — separate from Time in the site IA.

Why do Thanksgiving and Memorial Day move?

They follow holiday rules (fourth Thursday in November; last Monday in May). The clock always targets the next occurrence.

Is Tax Day always April 15?

Often, but IRS deadlines can shift for weekends or Emancipation Day. Confirm the filing year on IRS.gov — this page is a calendar helper.

Want elapsed time since a historical event?

Use How long ago for WWII, D-Day, the moon landing, and similar past anchors.